Help needed — Building a frequency sensor (RMS block limitation)

Hello PLECS forum,

I am designing a frequency sensor and have been attempting to use the built-in RMS block to detect the amplitude (peak) of an input sine wave. My attempt runs into the following problem:

Approach tried: Use the RMS block to infer peak amplitude of the input sine wave.

Problem faced: The RMS block computes RMS assuming a predefined/reference frequency, so it does not produce correct results for an input sine of unknown or varying frequency. As a result it fails to detect the peak reliably when the input frequency is not fixed.

Required behavior: I need a block with the same ease-of-use as the existing RMS block but which correctly senses RMS/peak for any unknown input frequency (i.e., frequency-independent RMS or a true instantaneous peak detector for sine waves).

Could someone please advise how to build or configure such a block in PLECS, or suggest alternative approaches (blocks/algorithms) that reliably measure RMS/peak for unknown-frequency sine inputs?

Thanks in advance for your help.

Hi Sourav,

Are you looking for a solution similar to How to identify the highest value of a signal over time? - #2 by Kris_Eberle ?

If however, you are looking at a grid connected converter and need to know the peak voltage of your grid you could use the PLECS “Single-Phase PLL” component.

Could you provide a bit more detail on the application? It would be easier to suggest a solution with more context. For example, a peak detection algorithm implemented on a digital microcontroller would be modeled differently than one for an analog peak detection circuit.

Hello Munadir ,

The reference you provided helped me solve my problem…I was exactly searching for that algorithm that would let me detect the global maxima of a time varying function in its total simulation…and it it helped me eventaully to build a accurate frequency sensor…where I even replaced the C script derivative block with my own designed derivative algorithm..its giving quite accurate frequency detection…independent of the input amplitude or phase angle..

Thanks a lot…

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